Artificial system for vision and the like

ABSTRACT

An artificial system for vision and the like, in which a camera views an object and creates signals corresponding thereto which are conveyed to the nervous system of the subject, in which observation, control and improvement of the system is achieved by providing a display which enables the supervisor to simultaneously see what the camera sees at any particular moment and what sensations the subject experiences, and to determine the relative locations of the sensations in the nervous system of a particular subject by producing individual sensations in a particular sequence and spatially locating the sensations in a particular fashion with the assistance of the subject.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to improvements in artificialsystems for vision and the like which produce sensations such asphosphenes in the subjects. (The term “subject” is here used to refer toan individual, such as a totally or partially blind individual, usingthe system in question.)

[0002] It has long been known that a blind individual can be made toperceive a truly visual sensation when stimulations such as brief pulsesare applied to electrodes implanted in contact with the nervous systemof the subject. A pulse or train of pulses directed to a given electrodeconnected to a unique location results in the stimulated perception bythe subject of a spot or cluster of light, called a phosphene, at itsown particular location. A relatively small number of phosphenes createdby stimulation of electrodes appropriately selected from an implantedarray will present to the subject a pattern of light corresponding tothat which, at any given instant, a camera aimed by the subject, as bybeing attached to his head, “sees”. (The term “camera” is here used inits broadest sense to denote a device which senses [“sees”] a particularobject or series of objects and produces a corresponding set ofsignals.)

[0003] Those signals are, in a known artificial vision system, conveyedthrough the subject's skull to a series of individual electrodes incontact with predetermined spots at appropriate locations of thesubject's brain cortex, whether the visual cortex or the associationcortex, each such electrode, when appropriately energized by a receivedsignal, producing a uniquely located phosphene sensed by the subject.The selection of individual electrodes to be signal-energized at anyparticular moment defines the stimulated image corresponding to what thecamera senses. The subject, aware of the phosphenes existing at anygiven moment, thus “sees” something which to him represents a particularobject or shape.

[0004] Recently significant improvements have been made in such systems,especially but not exclusively artificial vision systems, giving to thesubject an increasingly effective “sight”, and providing to thesupervisor of such systems and the designer of improvements therein agreater facility in understanding what the subject actually “sees” andto what extent that corresponds to actuality, so that potentialimprovements can more expeditiously be carried out and evaluated.

SUMMARY OF THE INVENTION

[0005] To create in the subject's brain a set of sensations whichrepresent a particular object or shape has presented a problem. To do sowith equipment which can be conveniently carried about by the subjectgreatly complicates the problem. This patent relates to recentimprovements in systems of this type which materially expand theirusability and practicability. Those improvements fall into two closelyrelated categories—matters directly affecting what the subject “sees”,and matters improving the ability of the designer-supervisor of thesystem to ascertain and evaluate how the system is actually functioningso as to guide him in making further improvements.

[0006] To these ends it has been found that the intelligibility andmeaningfulness to the subject of the phosphene-produced image issignificantly enhanced when (a) that image is caused to be a negativerather than a positive of what the camera senses—in other words, thedark and light portions of the camera-sensed object are reversed intolight and dark signal portions respectively—and (b) the edges of theviewed object are brightly outlined.

[0007] A meaningful image can be produced in the nervous system of asubject using only a limited number of available electrodes, thusreducing the signal-producing and -manipulating requirement of thesystem. Moreover, it has been found that the effectiveness of such animage can advantageously be improved by applying, for a given camerasignal, a series of similar pulses to each operative electrode. Throughthe use of a multiplexing circuit a given pulse is applied sequentiallyto each of a series of selected electrodes, that pulse is then reappliedsequentially to that series of electrodes, and so on, so that a givencamera signal is effectively utilized to energize a group of selectedelectrodes with sequential pulses.

[0008] Primarily because of weight and size considerations, the cameraused in a system of the type under discussion must be extremely simple.For example, in the artificial vision system presently in use the camerais a miniaturized TV camera carried by, and contained within, a singlelens area of what appears to be an ordinary pair of sunglasses.Optically such a camera is not very versatile and in particular cannotoptically magnify or modify that which it senses. However, I have foundthat if approximate circuitry is provided between the camera and theelectrodes on the subject's nervous system which will controllablymagnify the amplitude of the signal produced thereby, that will ineffect magnify the perceived object and thus produce a “zoom” effectupon the phosphene image, the area of which is fixed. That amplificationvariation can be under the control of the subject, who can then producethe “zoom” effect whenever and to whatever extent desired.

[0009] One problem with phosphene-produced images is that they appear tobe at no particular distance from the subject but instead to more orless float in space, whether the object they represent is close to or ata distance from the subject. This clearly limits the effectiveness ofthe image in advising the subject accurately with respect to the objectviewed. Rangefinders with variable audible output are known and could beused by blind subjects but they have the disadvantage of interferingwith the subject's normal hearing or other senses. That disadvantage isavoided, in accordance with the present invention, by causing thedistance sensed by the rangefinder to produce in the nervous system avisible distance indication—illumination of specific phosphenes torepresent specific distances (e.g., near, medium or far) or periodicvariations in the produced stimulation, for example, a variation inintensity in visible stimulation, and preferably a blinking on and off,at a rate corresponding to the sensed distance, thereby conveyingdistance-intelligence to the subject while at the same time notsignificantly interfering with the visual representation then beingconveyed to him of the object being viewed nor with his normal auditoryactivities.

[0010] In particular the data processing carried out by the system inquestion takes the signal produced by the camera, feeds it through alink to a sub-notebook computer, obtains a corresponding output from thesub-notebook computer and feeds that output to a micro-controller, thecorresponding output of the micro-controller being amplified beforebeing applied selectively to the electrodes in the subject's nervoussystem.

[0011] There are several ways in which the supervisor-designer of thesystem may be kept aware in detail of the manner in which that system isoperating in order for that individual to be able to conceive of andimplement improvements. To that end, in the system of the presentinvention the camera is provided with means for indicating to thesupervisor-designer where the camera is pointed at any given point intime. That pointer may conveniently comprise a small laser sourceattached to the subject's sunglasses which produces a visible narrowlight beam which will impinge upon the object being viewed by thesubject. Further to the same end, the supervisor-designer is providedwith a dual display system which simultaneously exhibits for purposes ofcomparison what the camera actually sees and the correspondingconfiguration of the stimulations produced in the subject's brain.

[0012] Essential to such an evaluation in a particular artificial visionsystem is an accurate map setting forth, as precisely as possible, thelocation of each phosphene or group of phosphenes in the subject's“sight” corresponding to a given electrode. Phosphene maps have beenmade in the past by energizing a particular electrode and asking thesubject to state or indicate where the phosphene thus produced islocated. This is not as easy as it sounds because phosphenes as a groupsometimes move about in the subject's visual field and because objectivestatements from the subject as to where a particular phosphene islocated are often vague and sometimes misleading. According to thepresent invention a more accurate phosphene map, not as subject to suchvagaries, is obtained by first energizing two selected electrodes toproduce two separated reference phosphenes to define a reference line,such as a vertical line, then individually energizing additionalelectrodes each producing its own associated phosphene, and obtainingfrom the subject an estimate of the position of that additionalphosphene relative to the two originally selected referenced phosphenesand to the reference line which the latter define.

[0013] Each of these improvements enables and enhances the functioningof a system such as an artificial vision system effective to promoteindividual mobility. The cumulative effect of these improvements givesrise to a significant step forward in such artificial sensing systems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a pictorial view of the head of a subject utilizing anartificial vision system including the improvements of the presentinvention and showing the camera and the laser pointer mounted onsunglasses worn by the subject;

[0015]FIG. 2 is a side pictorial view of a subject showing the computerand electronics package which the subject carries;

[0016]FIG. 3 is a block diagram of a typical system;

[0017]FIG. 4 is an enlarged planar view of the electrode layout asapplied to the surface of the subject's brain;

[0018]FIG. 5 is a typical map in visual space of some of the phosphenesproduced by particular electrodes of the array of FIG. 4;

[0019]FIG. 6 is a photographic view of a particular test scene to beviewed by a subject; and

[0020]FIG. 7 is a representation of what the subject preferably “sees”when he views the test scene of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] While many of the improvements here disclosed and claimed areapplicable to several different types of artificial sensing systems,they are here specifically described as embodied in the at presentpreferred embodiment, a particular artificial vision system.

[0022] As may best be seen in FIGS. 1 and 2, the subject is providedwith a camera generally designated A which, for convenience, is mountedon the right lens 2 of a pair of sunglasses 4 worn by the subject. Thatcamera is electrically connected to a computer and electronics packagegenerally designated B carried by the subject, that package having anoutput cable 6 which is connected through the subject's scalp to anarray of electrodes generally designated C and shown in FIG. 4 implantedon the subject's brain, either on the visual cortex or the associationcortex. The associated circuitry and particularly the associatedsoftware, converts what the camera A “sees” into electric signalsapplied to selected electrodes of the array C, thereby to produce in thesubject's consciousness a series of phosphenes. The location of thephosphene or phosphenes associated with a particular electrode does notcorrespond to the location of that electrode on the array C, and henceit is necessary to ascertain, for each such electrode, where theassociated phosphene or phosphenes as sensed by the subject are located.This must be done in order to direct the signals produced by the cameraA to the appropriate electrodes so as to produce for the subject a groupof phosphenes representing what the camera “sees”. FIG. 5 represents atypical map in visual space showing the location, for one subject, ofthe phosphenes associated with certain selected electrodes identified bycorresponding number in FIG. 4.

[0023] When stimulated, each electrode produces perhaps 1-4 closelyspaced phosphenes. Each phosphene in a cluster ranges in size up to thediameter of a pencil at arms length. Neighboring phosphenes in eachcluster are generally too close to the adjacent phosphenes for anotherphosphene to be located between them.

[0024] The electrical connection between the electrodes of the array Cand the appropriate locations on the brain of the subject is preferablyaccomplished through the use of a platinum foil ground plane perforatedwith a hexagonal array of 5 mm. diameter holes on 3 mm. centers. Flatplatinum electrodes 1 mm, in diameter are centered in each hole. Thisground plane confines all current to a location beneath the dura, thuseliminating discomfort due to dural excitation when stimulating somesingle electrodes and when other arrays of electrodes are stimulatedsimultaneously. The ground plane also eliminates most phospheneinteraction when multiple electrodes are stimulated simultaneously, andprovides an additional means of electrical safety that is not possiblewhen stimulating between cortical electrodes and a ground plane outsidethe skull. Each electrode is connected by a separate teflon insulatedwire to a connector contained in a percutaneous pedestal accessible atthe interior of the subject's scalp.

[0025] As shown in FIG. 3, the signals produced by the camera A—normalconventional television signals—are fed to link 6, such as the knownNational Television Standard Committee (“NTSC”) link, which converts thenormal television signal to a digital video signal that a computer can“understand”. The output of that link 6 is fed to a sub-notebookcomputer 8, which in turn feeds a micro-controller and stimulusgenerator 10, which in turn produces the signals to select and stimulatethe appropriate electrodes of the implanted array C.

[0026] In a preferred embodiment the camera A is a 492×512 pixel CCD(Charge-Coupled-Device”) black and white television camera powered by a9 volt battery. This f 14.5 camera has a 69° field of vision andutilizes a pinhole aperture instead of a lens to minimize size andweight. It also incorporates an electronic “iris” for automatic exposurecontrol.

[0027] The sub-notebook computer 8 incorporates a 233 MHz microprocessorwith 32 MB of RAM and a 4.0 GB hard drive. It also has an LCD screen andkeyboard. It was selected because of its very small size and lightweight. The belt pack B contains the link 6, the sub-notebook computer8, the micro-controller 10 and associated circuitry and software. Thecomputer and electronics package together are about the size of adictionary and weigh approximately 10 pounds, including camera, cables,and rechargeable batteries. The battery pack for the computer willoperate for approximately 3 hours and the battery pack for the otherelements will operate for approximately 6 hours.

[0028] Stimulation delivered to each electrode typically consists of atrain of six pulses delivered at 30 Hz to produce each frame of theimage. Frames have been produced with 1-50 pulses, and frame rates havebeen varied from 1 to 20 frames per second. Frame rates of 4 per secondcurrently seem best, even with trains containing only a single pulse.Each pulse is symmetric, biphasic (−/+), with a pulse width of 500 usecper phase (1,000 usec total). Threshold amplitudes may vary +/− 20% fromday to day; they are higher than the thresholds of similar electrodeswithout the ground plane, presumably because current shunts across thesurface of the piarachnoid and encapsulating membrane. The system iscalibrated each morning by re-computing the thresholds for eachelectrode, a simple procedure that takes the volunteer approximately 15minutes with a numeric keypad.

[0029] In order to extract intelligence from the camera segment it isnot necessary to use all of the 64 electrodes that are provided in theinstallation illustrated in FIG. 4, but as a practical matter aplurality of such electrodes must be simultaneously energized if ameaningful phosphene image is to be produced. It has been found that asfew as 10 electrodes need be energized to produce a particular frame.With an appropriate pulse width and pulse frequency it is possible toenergize the desired number of electrodes from a single drive byutilizing the time slots between the pulses destined for one electrodeto receive pulses selected for a series of other electrodes. This isreadily accomplished by using a conventional demultiplexer circuit inreverse. The conventional demultiplexer circuit accepts a series ofinputs and feeds them in predetermined order to a single output. As usedhere, the demultiplexer circuit will take a single input signal and feedit seriatim to a number of outputs corresponding to the desired numberof electrodes to be energized. Thus the multiplexer circuit will feed afirst pulse to a series of electrodes in order, it will then feed asecond pulse to the same series of electrodes preferably in the sameorder, and so on. The frequency at which the pulses are produced and thewidth of those pulses determine the intervals of time available forpulses to be directed to a selected series of electrodes.

[0030] Brightness of the phosphenes can easily be modulated by changesin pulse amplitude. However, provision of “gray scale” has not provenvery valuable so far, probably because of the combination of tunnelvision and limited resolution.

[0031] The phosphene display is planar, but is of uncertain distance,like the stars, in the sky. This presents to the subject a problem indepth perception. It is normally difficult for him to determine whetherone sensed object is at the same distance from the camera as anothersensed object. Ultrasonic rangefinders have been known for many yearsand have been used by the blind. Conventionally such rangefinderstranslate sensed distance into normally sensed signals such as audiosignals, but those normally sensed signals interfere with the ability ofthe subject to use his sense of hearing or other sense in its normalfashion. In accordance with the present invention, to overcome thatdisadvantage an ultrasonic rangefinder may be utilized with the presentsystem, as, for example, being secured to the left lens 10 of thesunglasses 4, but the output of that rangefinder is caused to give risein the nervous system to a visible distance indication—illumination ofspecific phosphenes to represent specific distances (e.g., near, medium,or far) or periodic variations in the produced stimulation, for examplea periodic variation in brightness, and preferably a blinking on andoff, at a rate corresponding to the sensed distance. Thus the acuity andintelligibility of the subject's sense of hearing is not compromisedalthough the subject is given an indication of the relative distance tovarious objects.

[0032] The camera A must be small, light and inconspicuous if it is tobe carried by the sunglasses 4. Such a camera is necessarily opticallysimple. For example, the camera 2 disclosed in FIG. 1 has a non-variable69° field of vision and any attempt to alter its field of vision or toprovide a “zoom” feature would involve heavy and conspicuous equipment,which is of course contraindicated. However, if the system between thecamera A and the electrode array C is provided with appropriatecircuitry to controllably magnify the amplitude of the stimulation,magnification of the signals fourfold or more will produce an imagewhich, because the field of vision is limited, exceeds the tunnellimitation of the camera, thus producing a “zoom” effect. Theamplification can be under the control of the subject if desired.

[0033] One limitation on the intelligibility of phosphene images in thesubject's brain is the number of frames that can be sequentially createdin a given period of time. The greater the number of frames in a periodof time the more intelligence is transmitted to the subject, but thegreater are the demands which are placed on the system, and the systemis essentially limited by the state-of-the-art and the necessity that itbe readily portable by the subject. Producing one frame per second istoo slow to provide good mobility to the subject, and merely increasingthe frame rate, all else being constant, does not itself produce anphosphene image of appropriate clarity. These problems have been greatlyameliorated by two steps—darkness inversion and edge detection. Darknessinversion means that the signal from the camera A is in effect reversedor inverted, so that dark-sensed portions of the camera-viewed imageresult in light-producing signals applied to the electrodes andlight-sensed portions of the camera-viewed image result indark-producing signals applied to the electrodes. Edgedetection—producing an image in which edges are sensed andintensified—is a known procedure in other contexts. When edge detection,particularly using Sobel filters, is employed in a system of the typeunder discussion, and particularly when it is used in conjunction withdarkness inversion, that permits processing and transmitting images in a233 MHz system at, a speed up to 8 frames per second with existingequipment, which in turn results in greatly improved transmissions ofintelligence to the subject. FIGS. 6 and 7 are illustrative of theeffects thus achieved. FIG. 6 discloses a typical demonstration set upcomprising a mannequin 12, a cap 14, and three different sockets 16, 18,and 20 mounted on a wall 22. With darkness inversion and particularlywith edge detection the resultant phosphene image is as shown in FIG. 7.Sensing an image of the type disclosed in FIG. 7 the subject is easilyable to find the mannequin and the cap and to detect the sockets.Similarly, doorways would appear as an outline of white phosphenes on ablack background, making the location of the doorway very clear to thesubject.

[0034] Important to the operation and particularly the improvement ofthe system is the ability of the supervisor or designer of the system toknow precisely how the system is operating, what it is accomplishing andwhat it is not accomplishing the system of the present invention isprovided with several new features to improve supervision and facilitateimprovement of design.

[0035] For example, it is important that the supervisor-designer(hereinafter generically designated “operator”) know what particularphosphene pattern or other stimulation is being presented to the subjectat any given moment. To that end, and as shown in FIG. 3, thesub-notebook computer 8 may not only send intelligence to themicro-controller 10 but also send it to an RF transmitter 26 which iselectromagnetically linked at 28 with RF receiver 30 which in turn islinked to a VCR and monitor 32. Hence the monitor 32 lets the operatorknow what the subject is “seeing”. Simultaneously a display may show tothe operator what the camera A is seeing. In its preferred form the twodisplays—what the camera sees and the corresponding phosphene map—may beprovided on a split screen for convenient comparison.

[0036] Along the same lines, it is helpful to the operator, as heobserves the subject using the system, to know precisely in whatdirection the subject is “looking” at any given moment, that informationto be correlated with the displays just described, observation of thephysical movements of the subject, or otherwise. To that end, and as maybe seen in FIG. 1, the sunglasses 4 worn by the subject carry on atemple piece a laser generator 38 which emits a narrow beam of lightdirected in the same direction as that in which the subject is lookingand which therefore will produce a visible spot of light at theappropriate point on the scene being viewed.

[0037] The phosphene map is produced by selectively energizingparticular electrodes and asking the subject to identify the location ofthe phosphene as he sees it. This procedure is complicated by the factthat all phosphenes are produced in a relatively small area, which makespointing difficult, and that difficulty is compounded by the fact thatphosphenes move with movement of the subject's eye. Accuracy of thephosphene map for each subject is important in selecting the particularelectrodes to be energized at any given moment in order to produce inthe subject's brain an accurate image of what the camera is “seeing”. Inorder to produce a more accurate phosphene map a new procedure has beencreated—first two pre-selected electrodes are energized to produce twospaced phosphenes which define a reference line, generally but notnecessarily vertical. Then while those two phosphenes continue to beproduced, other individual electrodes are individually energized and thesubject is asked to identify the location of the phosphene thus producedrelative to the locations of the two original phosphenes and thereference line which the latter define. This is usually done in terms ofthe vertical spacing between each individually produced phosphene andthe two reference phosphenes as well as the distance of the individuallyproduced phosphene to one side or the other of the reference lineconnecting the original phosphenes. In this way, a more accuratephosphene map is produced.

[0038] With a system of the type here disclosed a blind subject isreadily able to navigate among a “family” of three mannequins—standingadult male, seated adult female and standing 3-year old child—randomlyplaced in a large room, without bumping into any of them. He can thenretrieve a cap which has been placed on a wall in a random location, andcan place that cap on the head of a designated mannequin. Subjects areable to recognize and identify characters in various standardized formsused in acuity tests, such as Snellen letters, Landolt links and Leafigures displayed to the subjects as pure black figures on a pure whitebackground of a size corresponding to a visual acuity of approximately20/2400.

[0039] The conversion of camera signals or other signals intoappropriate electrode pulses is accomplished by means of circuity andparticularly software which is state-of-the-art.

[0040] The artificial vision system in its present stage of developmenthas not yet been perfected to the degree that it will permit the subjectto read easily, but it does give the subject sufficient intelligence sothat he can move about safely and perform various physical tasks. By wayof example, a subject provided with a system of the type here describedhas not only been able to move about an apartment but has even been ableto enter a subway station and determine the location of the doors on atrain that has pulled into the station.

[0041] While a limited number of embodiments of the present inventionhave been here specifically disclosed, which can function individuallyor cumulatively, and many of which are not limited to use in anartificial vision system, it will be apparent that many variations maybe made therein, all without departing from the spirit of the inventionas defined in the following claims.

I claim:
 1. In an artificial sensing system comprising producing firstsignals corresponding to light and dark portions of a particular objectto be sensed and conveying to the nervous system of the subject secondsignals producing sensations in said nervous system corresponding atleast in part to said object; the improvement which comprises convertinglight-corresponding and dark-corresponding portions of said first signalinto dark-corresponding and light-corresponding portions respectively ofsaid second signal.
 2. In an artificial sensing system in which aparticular object is sensed and at least some light and dark portions ofsaid object are converted into signals which are conveyed to the nervoussystem of a subject to produce sensations corresponding at least in partto said object; the improvement which comprises sensing light and darkportions of said object and causing said sensation-producing signals torepresent an inversion of said light and dark portions of said objectinto dark and light portions thereof respectively.
 3. In an artificialsensing system in which a particular object is sensed and at least someportions of said object are converted into electrical signals which areconveyed to the nervous system of a subject to produce phosphenescorresponding at least in part to said object; the improvement whichcomprises causing the phosphenes produced by said signals to produce insaid subject's brain a comparatively bright outline of the image of saidobject when compared to the produced image of the remaining portion ofsaid object.
 4. In an artificial sensing system comprising creating aplurality of sensations in the nervous system of the subjectcorresponding to a particular object to be viewed by stimulating acorresponding plurality of electrodes electrically connectedrespectively to appropriate locations of the subject's nervous system;the improvement which comprises, for a given view of said object,providing for each of a plurality of selected electrodes a given signalcomprising a plurality of time-spaced pulses, and applying those pulsesto those electrodes through a multiplexer effective to accept a givensignal, convert said signal to a plurality of pulses for each selectedelectrode, and apply the first of those pulses sequentially to saidelectrodes, then the second of those pulses sequentially to said secondelectrode, and so on.
 5. In an artificial sensing system comprisingcreating a plurality of sensations in the nervous system of the subjectcorresponding to a particular object to be viewed by stimulating acorresponding plurality of electrodes electrically connectedrespectively to appropriate locations of the subject's nervous system;the improvement which comprises, for a given view of said object,providing for each of a plurality of selected electrodes a given signalcomprising a plurality of time-spaced pulses, and applying those pulsesto those electrodes through a multiplexer effective to accept a givensignal, converting said signal to a plurality of pulses for eachselected electrode, and applying those pulses sequentially to saidelectrodes one electrode at a time, a first pulse being appliedsequentially to one electrode at a time, a second pulse then beingapplied sequentially to one electrode at a time, and so on.
 6. In anartificial sensing system comprising creating in the nervous system of asubject sensations corresponding to a particular object to be viewed,thereby to produce for said subject a sensed representation of thatobject; the improvement which comprises providing the subject with arangefinder effective to detect the distance from the subject to saidobject and indicate to the subject what that distance is by causing thestimulation produced in the subject to sensibly reflect said distance,thereby conveying distance-intelligence to said subject while at thesame time conveying to said subject a visual representation of theobject in question.
 7. The artificial sensing system of claim 6 in whichsaid variation in stimulation is constituted by essentially blinkingsaid stimulation on and off at a rate corresponding to said distance. 8.To assist in the monitoring of an artificial sensing system whichcreates sensations in the nervous system of the subject corresponding toa particular object to be viewed by providing the subject with a camerawhich produces signals corresponding to the object to be viewed whichare converted into sensations in the subject's nervous system; theimprovement which comprises providing said subject with a deviceproducing a beam of light corresponding in direction to the direction inwhich said camera is pointed, thereby enabling those monitoring theactions of said subject to know what the camera is looking at any givenmoment.
 9. To assist in the monitoring of an artificial sensing systemwhich creates sensations in the nervous system of the subjectcorresponding to a particular object to be viewed by providing thesubject with a camera which produces signals corresponding to the objectto be viewed which are converted into sensations in the subject'snervous system; the improvement which comprises a display device whichproduces simultaneously viewable representations of (a) what the camerasees when viewing a particular object and, (b) a map representing thesensations then being present in the subject's nervous system.
 10. Toassist in the monitoring of an artificial sensing system which createssensations in the nervous system of the subject corresponding to aparticular object to be viewed by selectively stimulating a plurality ofelectrodes electrically connected respectively to appropriate locationsin the subject's nervous system and producing, when thus stimulated, oneor more sensations in particular locations in the subject's field ofconsciousness; the improvement comprising (a) energizing two selectedelectrodes to produce two separated reference sensations, (b) then,while keeping said reference sensations sensed by the subject,individually sequentially energizing additional electrodes tosequentially produce additional sensations each correspondingrespectively to the electrode then being energized, (c) for each suchadditional sensation obtaining from the subject an estimate of therelative position of said additional sensation relative to saidreferenced sensations, and (d) mapping the estimated positions of saidsensations.
 11. To assist in the monitoring of an artificial sensingsystem which creates sensations in the nervous system of the subjectcorresponding to a particular object to be viewed by selectivelystimulating a plurality of electrodes electrically connectedrespectively to appropriate locations in the subject's nervous systemand producing, when thus stimulated, one or more sensations in aparticular location in the subject's field of consciousness; theimprovement comprising (a) energizing two selected electrodes to producetwo separated reference sensations to define a reference line, (b) then,while keeping said reference sensations sensed by the subject,individually sequentially energizing additional electrodes tosequentially produce additional sensations each correspondingrespectively to the electrode then being energized, (c) for each suchadditional sensation obtaining from the subject an estimate of thevertical spacing of each additional sensation relative to the tworeferenced sensations and an estimate of the distance of said additionalsensation to one side or the other of said reference line, and (d)mapping the estimated positions of said sensations.
 12. In an artificialsensing system comprising creating a plurality of sensations in thenervous system of the subject corresponding to a particular object to beviewed by producing a series of signals corresponding to the object tobe viewed and converting those signals into sensations in the subject'snervous system; the improvement which comprises providing a variablesignal amplifier active on said signals before they are converted intosensations, and varying the degree of signal amplification thusproduced, thereby to vary the area of said object producing saidsensations and thus giving rise to a “zoom” effect.
 13. The artificialsensing system of claim 12 in which the variation in said magnificationis under the control of the subject.
 14. In an artificial sensing systemwhich creates sensations in the nervous system of the subjectcorresponding to a particular object to be viewed by providing thesubject with a device which produces a signal corresponding to an objectto be viewed and circuitry conveying said signals to electrodesconnected to particular areas of the subject's nervous system, therebyto produce sensations in said nervous system; the improvement whichcomprises obtaining from said device a first signal corresponding tosaid object, feeding said, first signal through a link and thencethrough a sub-notebook computer, feeding the output of the sub-notebookcomputer to a micro-controller and amplifying the output of the latterto electrodes corresponding to phosphene positions in the subject'sbrain.
 15. In the artificial sensing system of claims 1,electromagnetically coupling an output of said sub-notebook computer toa visual display device and thus creating a visible representation ofsaid object.